Seven youths, most students, have been arrested over the killing of a 22-year-old man thought to have been beaten to death after a trivial argument at a Mid-Autumn Festival barbecue in Chai Wan. The seven males, aged between 14 and 19, were arrested on Monday less than 12 hours after the body of Wong Siu-ngai was discovered on a grass pitch in Chai Wan about 6.30am on Monday, police said. The arrests were made when officers raided several locations in Chai Wan. The seven were still being held for questioning last night and no charges had been laid. Detectives are understood to be seeking other youngsters over the killing, which has been classified as murder. Officers were still investigating how many people attacked the victim, whose body was found near Pamela Youde Nethersole Eastern Hospital at the junction of Tai Tam Road and Chai Wan Road. 'Preliminary investigation revealed that the assault was provoked in a dispute over a trivial matter,' a police source said. 'The victim was punched and kicked. His head was badly beaten. He might have been beaten to death.' No weapon is thought to have been used. Another source said the suspects were acquaintances of the victim but not close friends and the dispute was thought to have broken out over Wong's behaviour. A post-mortem examination revealed the victim had died from a brain haemorrhage, a police spokeswoman said. About 3.30pm yesterday, one suspect, hooded and handcuffed, was escorted to the pitch. Wong, a delivery worker, was found dead in the centre of the pitch about 100 metres from a makeshift barbecue. Discarded items such as barbecue forks, paper dishes and newspapers were found around the stove. Police said Wong went for a barbecue with a group of friends, mostly students, late on Sunday. Investigations indicated the assault took place shortly after midnight when the victim argued with his friends, an investigator said. Wong was found unconscious in the middle of the grassland by an elderly man who was walking through the park shortly before 6.30am for morning exercise. He summoned paramedics. Wong was declared dead at the scene. Wong lived with his parents and younger brother in Sau Mau Ping.